Internet access. Good morning.I can not add my new PC which runs Vista to my existing home

Question

Good morning.I can not add my new PC which runs Vista to my existing home wireless network.I have used a memory stick to transfer set-up data and put in a WEP security code but to no avail.Is there something else I need to do ? There is a wireless adapter card in the PC but the little light does not come on or flash.Can you help ?Steve, N.Ireland